The invention relates to a technique and device for increasing the number of colors output by an active liquid crystal display.
Active color liquid crystal (LCD) displays, also known as Thin Field Transistor (TFT) panel displays, are commonly used in laptop computers to present information to a user. Active color LCD panels and color cathode-ray tube (CRT) monitors both have a color resolution that depends upon the number of pixels in the display. Typical active color LCD display resolutions are 640 columns of pixels by 480 rows of pixels (640.times.480), 800.times.600 pixels and up to 1280.times.1024 pixels. However, a CRT monitor uses analog data to form images on its screen, and an active color LCD panel display uses digital data.
Each pixel in the active color LCD display consists of three primary color components: red, green and blue. The four common types of active color LCD displays are known as 3-3-3, 4-4-4, 6-6-6 and 8-8-8 TFT panels. The numbers indicate the number of bits of data that must be supplied to each of the primary color components of a pixel in the display. For example, in a 3-3-3 TFT panel, 3 bits of data are required for each of the three pixel components, and thus each pixel component is capable of 2.sup.3 or eight levels of color. Consequently, the total color output of a pixel in the 3-3-3 panel equals 8.times.8.times.8 which is 512 colors.
New data must be supplied to the pixels of an active color LCD display periodically to refresh the image shown on the screen, and such time segments are known as frames. The required number of bits of data per pixel color component is typically supplied every 1/60th of a second, which corresponds to a refresh rate of sixty frames per second.
A technique known as frame modulation, which entails switching certain pixel color components ON and OFF over certain areas on the screen for a number of frames of the refresh cycle, is known for increasing the number of grey levels and thus the number of colors that can be shown on a color display. However, frame modulation has not been used to increase the number of colors output by an active LCD display because the pixel components change so quickly that using frame pattern modulation could result in noticeable flicker. A need exists, therefore, not only for increasing the number of colors that may be displayed by an active color LCD display, but also for improving the overall quality of the color and for minimizing any flicker of the screen which can be detected by the human eye.